The present invention relates to the field of photography and, more particularly, to folding cameras having a mirror in the exposure optical path and also including a self-erecting and folding viewfinder for viewing and framing the scene to be photographed.
Integral self-developing film units of the general type disclosed in commonly-assigned U.S. Pat. Nos. 3,415,664; 3,594,165 and 3,761,268 and marketed by Polaroid Corporation, Cambridge, Mass., under the tradename SX-70, Time Zero and 600 High Speed Land film, are exposed and viewed through the same side of the film unit thereby requiring an odd number of image reversals in the exposure optical path for correct image orientation.
Most commonly, cameras designed for this type of film include a horizontal base section for supporting a film pack with the forwardmost film unit therein located at the camera's film or exposure plane; an upstanding lens and shutter housing located at the forward end of the base section and mounting an objective lens with its optical axis generally parallel, or at some other non-perpendicular angle, to the film plane; and a mirror mounted at the opposite end of the base section with its forwardly directed reflective surface inclined at an appropriate angle with respect to the film plane and lens axis to reflect image forming light from the lens down onto the film unit for exposure. The mirror thus provides the necessary additional image reversal and also allows the relatively long optical path required for focusing an image on a snapshot sized film unit to be folded thereby making the camera more compact in its exposure configuration.
Representative examples of folding cameras of this general type having a variety of different folding viewfinders or viewfinder assemblies may be found in U.S. Pat. Nos. 3,479,941; 3,589,253; 3,683,770; 3,722,389; 3,877,046 and 4,166,683.
Typically, these cameras include a base section, a lens and shutter housing pivotally coupled to one end of the base section, a cover section supporting the mirror, pivotally coupled to the opposite end of the base section, and a folding bellows disposed therebetween. When the camera is erected, the lens and shutter housing is located in upstanding relation to the forward end of the base section and the cover station is inclined upwardly to set the mirror at the proper angle with respect to the lens axis and the film plane in the base section. The bellows is erected between the housing sections to block ambient light from the exposure optical path.
As the camera is folded, the lens and shutter housing pivots forwardly and downwardly in front of the forward end of the base housing section to assume its storage position in substantially coplanar end-to-end relation therewith and the cover section folds down into overlying relation with the base section. The bellows folds into a flat configuration and is stored therebetween.
A common basic design feature in the folding schemes employed in all of the cameras disclosed in the above-noted patents is that the two largest (by volume) housing sections--the base housing section for receiving the film pack and the lens and shutter housing--are arranged in longitudinally extending, generally coplanar end-to-end relation when the camera is in its folded position. This maximizes the length of the folded camera in the interest of minimizing its height or thickness dimension.
The relative folded storage positions of these two major housing sections determines the overall philosophy of the camera folding scheme into which the other components--cover housing section, mirror, bellows and viewfinder--must be integrated in a compatible manner.
The above-noted prior art cameras employ a variety of different types of viewfinders or viewfinder assemblies which are integrated into the folding scheme in a manner that is compatible with the end-to-end placement of the base section and lens end shutter housing.
For example, the cameras disclosed in U.S. Pat. Nos. 3,479,941 and 3,683,770 have a unified elongated direct viewfinder built into the side of the cover housing section for movement therewith between the erected and storage positions. The term "unified viewfinder" means that all of the viewfinder optical elements are mounted on a common structure and move as a unit, while remaining in optical alignment, when the camera is folded and erected.
The camera disclosed in U.S. Pat. No. 3,589,253 mounts a unified viewfinder on an elongated movable erecting link and includes a recess provided at the trailing end of the cover section for receiving the viewfinder therein when the camera is folded. In U.S. Pat. No. 3,877,046, the unified viewfinder is mounted on and moves with the lens and shutter housing.
Other cameras of this type are provided with a divided viewfinder assembly wherein front and rear optical elements, or groups of elements, are mounted on different camera components for independent movement between a folded storage position where the elements are not in functioning optical alignment and an operative erected position wherein the elements are in optical alignment to form the viewfinder.
For example, the camera disclosed in U.S. Pat. No. 3,722,389 employs a single lens reflex viewing system wherein light trasmitted through the objective lens is reflected from a mirror onto a viewing and focusing screen and then to a viewfinder assembly comprising an asymmetric mirror and rear eyelens. The objective lens is mounted on the lens and shutter housing, the mirror is mounted on the cover housing section, the focusing screen is located in the base section over the film plane and the viewing assembly is mounted on a short cover section. The viewing assembly comprising the asymmetric mirror and rear lens is not completely self-erecting in that its overlying cover must be manually unlatched by the camera operator in preparation for erecting the camera and also must be manually folded and latched as the final step in locating the interconnected housing sections in the folded storage position. In U.S. Pat. No. 4,166,683, a front group of viewfinder lens elements are mounted on the lens and shutter housing to one side of the objective lens and a group of rear lens elements are aligned in a tubular structure that is pivotally mounted on the cover section. When the camera is erected, the front and rear groups are in optical alignment to form a direct viewing viewfinder. When the camera is folded, the forward group of lens elements rotates downwardly with the lens and shutter housing into its end-to-end relationship with the base section and the tube mounting the rear elements pivots into a storage position located between the base section and the closed cover section.
Obviously, for such a divided viewfinder to function effectively there must be good optical alignment between the front and rear optical elements or groups of elements when the camera is in its operative erected position.
The present invention relates to a folding camera that includes a mirror in the exposure optical path for providing correct image orientation in the final print but employs a folding scheme that differs from those described above in that the lens and shutter housing is configured to fold back over the base housing section to assume a folded storage position overlying the film plane. Thus, the two major housing sections are arranged in stacked, rather than in end-to-end, relationship to minimize the length of the folded camera while making it somewhat thicker.
Therefore, it is an object of the present invention to provide such a folding camera wherein the lens housing is folded back over the base section for storage and the other major components of the camera, including a self-erecting and folding viewfinder, are integrated therewith in a manner that is compatible with this folding scheme.
Another object is to provide such a camera that is simply constructed and easy to use.
Yet another object is to provide such a camera wherein the viewfinder is of the divide type and is structured to facilitate good optical alignment of the individual viewfinder optical elements when the camera is in its operative erected position.
Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.